The present invention relates to ink jet printing and, in particular, discloses a nozzle arrangement for an ink jet printhead.
Many different types of printing have been invented, a large number of which are presently in use. The known forms of printers have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Ink Jet printers themselves come in many different types. The utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electrostatic ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electrostatic field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al).
Piezo-electric ink jet printers are also one form of commonly utilized ink jet printing device. Piezo-electric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezo electric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezo-electric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a Piezo electric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a sheer mode type of piezo-electric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2,007,162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques relying upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
Recently, in Australian Provisional Patent Specification No. PP6534 filed Oct. 16, 1998 entitled xe2x80x9cMicromechanical Device and, Method (IJ46a)xe2x80x9d filed by the assignee of the present application, the contents of which are incorporated herein by way of cross reference, an ink jet printing system was disclosed having a series of chambers, each with a ink ejection nozzle aperture in one wall of the chamber. A moveable paddle activated by a thermal bend actuator is disclosed such that movement of the paddle causes a resultant ejection of ink from the chamber. The ink is then refilled via means of surface tension drawing fluid into the chamber.
In any printing arrangement, it is often desirable to operate the print head at a maximum throughput speed. In an ink jet printing arrangement, the limiting factor in the speed of operation is often the refill time of the chamber. It is desirable to provide as rapid a refill of the chamber as possible.
The present invention therefore provides a nozzle arrangement for an ink jet printhead, the nozzle arrangement comprising:
side walls and a roof wall that define an ink chamber and a nozzle aperture defined in the roof wall for the ejection of ink, the side walls and the roof wall being configured so that a cross sectional area of the ink chamber increases continually towards the nozzle aperture; and
a moveable paddle that is positioned within said chamber, said paddle being displaceable between a first distal position and a second proximal position with respect to the nozzle aperture to eject ink from the nozzle aperture.
Preferably, said side walls define a divergent profile.
Preferably, the nozzle arrangement is the product of an integrated circuit fabrication technique which includes a re-entrant etching process carried out on a sacrificial layer utilized in forming said side and roof walls.